What a profile they cut, slicing through the city: gorgeous, exotic, dangerous. You see them parked like emaciated steeds outside the coolest clubs.

They don't make much sense, yet for one more fleeting season at least, they are the rage in certain circles. Sort of dumb and super hip: the twin characteristics of many things in life.

We are talking about a bicycle. A very special kind of road bicycle, called a fixed-gear bike, or fixie for short.

A fixie has one speed, which makes it difficult to pedal uphill. A classic fixie has no brakes, which makes it difficult to slow on the downhill. A fixie has no freewheel, the part that makes coasting possible. Instead, the chain directly drives the rotation of the rear wheel, which means the pedals always turn while the bike moves.

What else do they have going for them?

Well, fixies are impractical, perverse throwbacks to a time more than a century ago, before the invention of the derailleur and the Tour de France, when the bicycle chain and the pneumatic tube were novelties, and the high-wheel penny-farthing "ordinary" bicycle had just been eclipsed by the chain-driven "safety" bike.

And yet despite all that -- or is it because of all that? -- a fixie manages the neat trick of simultaneously communicating taste and rebellion.

To each his own bicycle, in a town where bicycling is an ever-expanding religion, with many rival sects. But a fixie? Speak to us, pilgrims.

Jason Stevenson was one of Washington's earliest fixie converts. He remembers the first time he saw one. It was the leanest machine he had ever seen, a contraption almost completely unknown in Washington. He was spellbound.

"So clean, so fluid. I just had to have one," he says. "I was like, whatever bike that is, I want to ride something like that."

The year was 1993, and Stevenson was a bike messenger, as he is now.

He knew of only three messengers riding fixies then. Washington was a little behind the curve. Some date the dawn of fixie chic to the 1986 movie "Quicksilver," starring Kevin Bacon, which glorified fixie-riding messengers in New York.